import { BadRequestException, Injectable, Logger } from '@nestjs/common';
import {
  embedMany,
  experimental_transcribe as transcribe,
  generateText,
  type EmbeddingModel,
  type LanguageModel,
} from 'ai';
import { createOpenAI } from '@ai-sdk/openai';
import { createGoogleGenerativeAI } from '@ai-sdk/google';
import { createOllama } from 'ai-sdk-ollama';
import { AiSettingsService } from './ai-settings.service';
import { AiNotConfiguredException } from './ai-not-configured.exception';
import { AiEmbeddingNotConfiguredException } from './ai-embedding-not-configured.exception';
import { AiSttNotConfiguredException } from './ai-stt-not-configured.exception';
import { describeProviderError } from './ai-error.util';

/**
 * Builds AI SDK language models from per-workspace config and runs cheap
 * connectivity checks.
 *
 * The provider client is built PER WORKSPACE on demand — never cached globally —
 * and the decrypted API key is held only for the duration of the call and is
 * never logged (§6.2/§8).
 */
@Injectable()
export class AiService {
  private readonly logger = new Logger(AiService.name);

  constructor(private readonly aiSettings: AiSettingsService) {}

  /**
   * Resolve the workspace config and build the chat language model.
   * Throws AiNotConfiguredException (→ 503) when the config is incomplete.
   */
  async getChatModel(workspaceId: string): Promise<LanguageModel> {
    const cfg = await this.aiSettings.resolve(workspaceId);
    if (
      !cfg?.driver ||
      !cfg?.chatModel ||
      (cfg.driver !== 'ollama' && !cfg.apiKey)
    ) {
      throw new AiNotConfiguredException();
    }

    switch (cfg.driver) {
      case 'openai':
        // baseURL (when set) covers openai-compatible endpoints. Use Chat
        // Completions (/chat/completions) — the portable OpenAI-compatible
        // endpoint. The default callable createOpenAI(...)(model) targets the
        // Responses API (/responses), which OpenAI-compatible gateways
        // (OpenRouter, etc.) reject on multi-turn requests (history with
        // assistant messages) → 400.
        return createOpenAI({ apiKey: cfg.apiKey, baseURL: cfg.baseUrl }).chat(
          cfg.chatModel,
        );
      case 'gemini':
        return createGoogleGenerativeAI({ apiKey: cfg.apiKey })(cfg.chatModel);
      case 'ollama':
        // Ollama needs no API key.
        return createOllama({ baseURL: cfg.baseUrl })(cfg.chatModel);
      default:
        throw new AiNotConfiguredException();
    }
  }

  /**
   * Resolve the workspace config and build the text-embedding model used by the
   * RAG indexer / semanticSearch (§6.7 stage D). Built PER WORKSPACE on demand,
   * same as getChatModel; the decrypted key is never logged.
   *
   * Uses the embedding-specific endpoint/key (`embeddingBaseUrl` /
   * `embeddingApiKey`), which fall back to the chat values when unset (resolved
   * by AiSettingsService.resolve).
   *
   * Throws AiEmbeddingNotConfiguredException (→ 503) when the driver,
   * embeddingModel or (for non-ollama) the embedding API key is missing, so RAG
   * callers can 503 or skip independently of chat being configured.
   */
  async getEmbeddingModel(workspaceId: string): Promise<EmbeddingModel> {
    const cfg = await this.aiSettings.resolve(workspaceId);
    if (
      !cfg?.driver ||
      !cfg?.embeddingModel ||
      (cfg.driver !== 'ollama' && !cfg.embeddingApiKey)
    ) {
      throw new AiEmbeddingNotConfiguredException();
    }

    switch (cfg.driver) {
      case 'openai':
        // embeddingBaseUrl (when set) covers openai-compatible endpoints.
        return createOpenAI({
          apiKey: cfg.embeddingApiKey,
          baseURL: cfg.embeddingBaseUrl,
        }).textEmbeddingModel(cfg.embeddingModel);
      case 'gemini':
        return createGoogleGenerativeAI({
          apiKey: cfg.embeddingApiKey,
        }).textEmbeddingModel(cfg.embeddingModel);
      case 'ollama':
        // Ollama needs no API key (e.g. nomic-embed-text).
        return createOllama({ baseURL: cfg.embeddingBaseUrl }).textEmbeddingModel(
          cfg.embeddingModel,
        );
      default:
        throw new AiEmbeddingNotConfiguredException();
    }
  }

  /**
   * Transcribe audio with the workspace STT model. The request encoding is the
   * admin-chosen `sttApiStyle`: 'json' uses the JSON+base64 audio/transcriptions
   * API (OpenRouter); anything else (default 'multipart') uses the AI SDK
   * multipart path (OpenAI, speaches, faster-whisper-server, ...). `format` is
   * the audio container hint (webm / mp4 / wav / mp3 / ogg / m4a). Built PER
   * WORKSPACE; the key is never logged. Throws AiSttNotConfiguredException
   * (-> 503) when no STT model is configured.
   */
  async transcribe(
    workspaceId: string,
    audio: Uint8Array,
    format: string,
  ): Promise<string> {
    const cfg = await this.aiSettings.resolve(workspaceId);
    if (!cfg?.sttModel) throw new AiSttNotConfiguredException();
    const baseURL = cfg.sttBaseUrl || cfg.baseUrl;

    // Explicit, admin-chosen request encoding (no URL guessing). 'json' is the
    // OpenRouter style (JSON + base64 input_audio); everything else uses the
    // OpenAI-compatible multipart path via the AI SDK.
    if (cfg.sttApiStyle === 'json') {
      return this.transcribeJsonBase64(baseURL, cfg.sttApiKey, cfg.sttModel, audio, format);
    }

    // Standard OpenAI-compatible multipart path (AI SDK). apiKey may be unused for
    // keyless self-hosted whisper; pass a placeholder.
    const model = createOpenAI({
      apiKey: cfg.sttApiKey ?? 'unused',
      baseURL,
    }).transcription(cfg.sttModel);
    const { text } = await transcribe({ model, audio });
    return text.trim();
  }

  /**
   * JSON + base64 transcription body (OpenRouter-style). POSTs
   * { model, input_audio: { data, format } } to {baseURL}/audio/transcriptions
   * and returns { text }.
   */
  private async transcribeJsonBase64(
    baseURL: string | undefined,
    apiKey: string | undefined,
    model: string,
    audio: Uint8Array,
    format: string,
  ): Promise<string> {
    if (!baseURL) {
      throw new BadRequestException(
        'STT base URL is not set (required for the JSON request format)',
      );
    }
    const url = `${baseURL.replace(/\/$/, '')}/audio/transcriptions`;
    const res = await fetch(url, {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
        ...(apiKey ? { Authorization: `Bearer ${apiKey}` } : {}),
      },
      body: JSON.stringify({
        model,
        input_audio: {
          data: Buffer.from(audio).toString('base64'),
          format,
        },
      }),
    });
    if (!res.ok) {
      // Surface status + body so the real reason reaches the user; never log the key.
      const body = await res.text().catch(() => '');
      throw new Error(
        `JSON transcription request failed (${res.status}): ${body.slice(0, 500)}`,
      );
    }
    const json = (await res.json()) as { text?: string };
    return (json.text ?? '').trim();
  }

  /**
   * Embed a batch of texts with the workspace embedding model. Returns one
   * vector per input, in the same order. Thin wrapper over the AI SDK's
   * embedMany; never logs the key or the texts.
   */
  async embedTexts(workspaceId: string, texts: string[]): Promise<number[][]> {
    if (texts.length === 0) return [];
    const model = await this.getEmbeddingModel(workspaceId);
    // Bound the embedding call: a slow/hung embeddings endpoint must fail loudly
    // (and let the caller move on to the next page) instead of blocking forever.
    // The single signal caps the WHOLE call, including the SDK's internal
    // retries/backoff (embedMany defaults to maxRetries: 2).
    const timeoutMs = AiService.embeddingTimeoutMs();
    const signal = AbortSignal.timeout(timeoutMs);
    try {
      const { embeddings } = await embedMany({
        model,
        values: texts,
        abortSignal: signal,
      });
      return embeddings;
    } catch (err) {
      // AbortSignal.timeout aborts with an opaque TimeoutError; surface a clear,
      // greppable message so a hung/slow embeddings endpoint is obvious in logs.
      // Classify by the error itself (name) AND the signal, not the flag alone:
      // a genuine provider error that loses a race with the timer would also see
      // `signal.aborted === true`, and must keep its real diagnostics.
      // Mirror the SDK's own isAbortError (@ai-sdk/provider-utils): it treats
      // TimeoutError, AbortError and ResponseAborted (Next.js) as aborts.
      const abortLike =
        err instanceof Error &&
        (err.name === 'TimeoutError' ||
          err.name === 'AbortError' ||
          err.name === 'ResponseAborted');
      if (signal.aborted && abortLike) {
        throw new Error(
          `Embedding request timed out after ${timeoutMs}ms ` +
            `(workspace ${workspaceId}, ${texts.length} chunk(s)). ` +
            `Increase AI_EMBEDDING_TIMEOUT_MS or check the embeddings endpoint.`,
        );
      }
      throw err;
    }
  }

  /**
   * Per-embedding-call timeout in ms. Configurable via AI_EMBEDDING_TIMEOUT_MS;
   * falls back to 120000 (2 min) when unset or invalid.
   */
  private static embeddingTimeoutMs(): number {
    const raw = Number(process.env.AI_EMBEDDING_TIMEOUT_MS);
    return Number.isFinite(raw) && raw > 0 ? raw : 120_000;
  }

  // Build a tiny valid WAV (mono, 16-bit PCM, 16 kHz, ~1s of silence), used only
  // as a connectivity probe for the STT endpoint in testConnection.
  private static silentWavProbe(): Uint8Array {
    const sampleRate = 16000;
    const numSamples = sampleRate; // ~1 second
    const dataSize = numSamples * 2; // 16-bit mono
    const buf = Buffer.alloc(44 + dataSize);
    buf.write('RIFF', 0);
    buf.writeUInt32LE(36 + dataSize, 4);
    buf.write('WAVE', 8);
    buf.write('fmt ', 12);
    buf.writeUInt32LE(16, 16); // PCM fmt chunk size
    buf.writeUInt16LE(1, 20); // audio format = PCM
    buf.writeUInt16LE(1, 22); // channels = 1
    buf.writeUInt32LE(sampleRate, 24);
    buf.writeUInt32LE(sampleRate * 2, 28); // byte rate
    buf.writeUInt16LE(2, 32); // block align
    buf.writeUInt16LE(16, 34); // bits per sample
    buf.write('data', 36);
    buf.writeUInt32LE(dataSize, 40);
    // The PCM samples stay zero (silence).
    return buf;
  }

  /**
   * Cheap connectivity check for a single "Test endpoint" button. Probes ONLY
   * the requested capability so each card in the UI surfaces its own result:
   *  - `chat`: a one-word generation against the configured chat model;
   *  - `embeddings`: embedding a tiny string against the embedding model;
   *  - `stt`: transcribing a tiny silent WAV against the transcription model.
   *
   * A capability that is not configured returns a plain "… is not configured"
   * message; any real failure returns ok:false with the provider's own cause
   * (statusCode + truncated response body via describeProviderError). The
   * decrypted key is never logged or returned — AI SDK error fields do not carry
   * it, and the resolved config is never dumped.
   *
   * Probing embeddings here catches a misconfigured embeddings endpoint (e.g.
   * one returning non-JSON, which the background RAG indexer would otherwise hit
   * as an opaque "Invalid JSON response") at config time instead of silently
   * during indexing.
   */
  async testConnection(
    workspaceId: string,
    capability: 'chat' | 'embeddings' | 'stt' = 'chat',
  ): Promise<{ ok: true } | { ok: false; error: string }> {
    if (capability === 'embeddings') {
      try {
        await this.embedTexts(workspaceId, ['ping']);
        return { ok: true };
      } catch (err) {
        if (err instanceof AiEmbeddingNotConfiguredException) {
          return { ok: false, error: 'Embeddings are not configured' };
        }
        this.logger.error('AI embedding test connection failed', err as Error);
        return { ok: false, error: describeProviderError(err) };
      }
    }

    if (capability === 'stt') {
      try {
        // Probe with a tiny silent WAV; a reachable, authorized endpoint returns
        // (usually empty) text, any failure surfaces via describeProviderError.
        await this.transcribe(workspaceId, AiService.silentWavProbe(), 'wav');
        return { ok: true };
      } catch (err) {
        if (err instanceof AiSttNotConfiguredException) {
          return { ok: false, error: 'STT is not configured' };
        }
        this.logger.error('AI STT test connection failed', err as Error);
        return { ok: false, error: describeProviderError(err) };
      }
    }

    // Default: chat probe.
    try {
      const model = await this.getChatModel(workspaceId);
      // maxOutputTokens keeps the probe cheap and avoids providers (e.g.
      // OpenRouter) reserving/charging for the model's full max-token budget,
      // which would 402 on a key with limited credit.
      await generateText({ model, prompt: 'ping', maxOutputTokens: 16 });
      return { ok: true };
    } catch (err) {
      if (err instanceof AiNotConfiguredException) {
        return { ok: false, error: 'Chat is not configured' };
      }
      this.logger.error('AI chat test connection failed', err as Error);
      return { ok: false, error: describeProviderError(err) };
    }
  }
}